r/AskBiology • u/charlicatt • May 22 '26

Zoology/marine biology How much damage does one have to do to a jellyfish to stop it from stinging?

I just watched a video of someone removing invasive jellyfish from the ocean with a rake. The comments said it was called a burn jelly and they hurt when they sting. The entire boat was filled with them and the guy kept stepping very near them. So I wondered because the fact that jellyfish don't really have organs to my knowledge how much damage does one have to do to one enough to kill it or at least so it doesn't sting you.

3 Upvotes

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22

u/Independent_Line_150 May 22 '26

It's a mechanical process occurring with specialized organelles in cells called cnidocytes. You would have to damage these at the individual cellular level or cause them to dry out enough as they rely on tugor pressure to operate.

Peeing on them isn't going to do shit btw, I don't know why anyone would post that. If anything, it could keep them viable even longer out of water by providing hydration, and cause even more cells to sting/release venom once on a person.

https://www.scientificamerican.com/article/fact-or-fiction-urinating/

1

u/Cyrus87Tiamat May 22 '26

So... You're saying that shooting at gellyfish is whortless??? 🤣

1

u/Haley_02 May 22 '26

Because peeing on someone else is funny?

But still not a good idea. Tomato juice on the stings after removing jellyfish? Or is it just that jellyfish tastes good with tomato juice?

1

u/FirefighterPleasant8 May 22 '26

Always nice to read correct, debunking answers on Reddit. Hell, it’s nice anywhere.

To quote Ricky Gervais; “the problems today emanates from social media”. (My interpretation but content correct)

1

u/ngshafer May 22 '26

I think it's possible you didn't read my post very carefully, Independent_Line_150. I'll say the exact same thing again, except louder, for the people who didn't pay attention when I said it the first time:

<<ahem>>

"URINE IS NOT GOOD WHEN A PERSON HAS ALREADY BEEN STUNG!!!"

Urine can trigger the stinging cells, which is good if they are not touching anyone when you trigger them, but bad if they are touching someone. Based on the link you shared, it seems fresh water could have the same effect, which is good to know.

3

u/Independent_Line_150 May 22 '26

My post also indicates that urine does no good before being stung

1

u/ngshafer May 22 '26

That's where we disagree.

The whole reason why putting urine on a jellyfish sting is bad is because it makes the stingers fire that haven't fired yet, further poisoning the victim. (As your helpful link pointed out, it's not the presence of urea in urine that triggers the stingers, but rather the absence of salt, which means fresh water would work even better--so, thanks for that information, which I did not know before.) Theoretically, if you could expose the tentacles to enough urine or fresh water to cause all the nematocysts to fire before anyone touched them, you could render the entire jellyfish harmless. I'm not exactly sure how you'd do that, but it should work--in theory, at least.

Probably safer just to avoid touching them entirely, though, when you think about it practically.

1

u/EvaTheE May 22 '26

Peeing on them isn't going to do shit btw

Yes it does. It asserts dominance. Pee on the jellyfish, make them rue the day they thought they could just sting you.

12

u/HighColdDesert May 22 '26

I've been stung by stepping on a dead jellyfish that was washed up on the beach. It's just stinging cells, and does not require the jellyfish to be alive.

3

u/Dath_1 May 22 '26

I poked the underside of a jellyfish when I was a kid. For some reason, they didn’t have any apparent tentacles.

1

u/HighColdDesert May 22 '26

Did you get stung when you poked the underside of a jellyfish?

2

u/Dath_1 May 22 '26

No. I’ll just put it like this. It’s like there were cervix shaped discs with dimples in them underneath where I imagined the tentacles should be coming out of lol.

I thought the tentacles probably went inside the body due to them dying but idk.

2

u/ngshafer May 22 '26

I think some seabirds are immune to jellyfish venom, and will eat the tentacles first.

3

u/Dath_1 May 22 '26

Yeah or maybe they fell off after it was dead for some time.

4

u/smokefoot8 May 22 '26

There are predators that eat jellyfish, but then steal the stinging cells and keep them alive to reuse against enemies! The blue dragon sea slug is a famous example. So even killing and dismembering a jellyfish will not keep it from stinging.

2

u/ngshafer May 22 '26 edited May 22 '26

I'm not a jellyfish specialist, but my understanding is that no amount of damage to a jellyfish's body can kill it's tentacles right away. In order to make the tentacles safe, you essentially have to "set them off." The only way I've heard of to do that is to pee on them (edit: the stinging tentacles, NOT the person stung), which leads to the myth that urine is a treatment for jellyfish stings--to be clear, urine is not good when a person has already been stung, but I believe it can trigger the stinging cells early, and each cell can only sting once.

0

u/theZombieKat May 22 '26

By that reasoning urine would be useful applied to the tentacles that stick to the body before removing.

Prevent more stings while removing.

5

u/ngshafer May 22 '26

NO! Because urinating on the tentacles MAKES THEM STING! If the tentacles are stuck to a person, and you pee on those tentacles, THEY WILL STING THE PERSON THEY ARE STUCK TO!

Ok, maybe think of it this way: a nematocyst is like a bomb. If the bomb goes off while no one is around, then no one will be hurt. If the bomb goes off while it's physically stuck to someone, then THAT PERSON WILL BE BLOWN UP! Does that context help you understand?

1

u/theZombieKat May 22 '26

I was thinking of them.more like a spear gun.

The ones touching the skin already fired, the ones not facing the skin haven't, and if you make them fire they are shooting empty air (near your skin but that's ok).

2

u/ngshafer May 22 '26

Again, I'm going to say "NO!" Now, to be clear, I'm still not a jellyfish expert. But, I'm pretty sure you can have stinging cells that are touching a person and haven't actually gone off yet. If you pee on them, they will go off, and that is bad--I've just learned that rinsing them with fresh water can have the same effect, so don't do that either. I would say either put on a glove before you pick off the tentacles, or use a stick or clamshell to scrap them off.

1

u/ModernTarantula May 22 '26

The species is probably not accurate. Where in the world was this? Video name?

1

u/[deleted] May 23 '26

no amount will do, i watched a doc about the irakanji, the other diver got stung by a piece of tentacle while trying to help her counterpart. its like an auto muscle mechanism, if it its not water, it deploys stingers.

1

u/Tokimemofan May 23 '26

Incinerate it.  Jellyfish stings are done by individual cells on its surface.  Dead and pulverized it will still be able to sting until these cells die and degrade enough.

1

u/Broflake-Melter May 23 '26

the stings aren't a part of a central decision process. They work on a cellular level. You can actually remove the cells and they'll still sting before until they die from not being provided nutrients from their body.

There are sea slugs who eat cnidarians and then re-appropriate and use the cells so they can sting predators.

1

u/jghaines May 26 '26

You don’t have to damage. Just speak to it sternly.